I don't have a solution to offer, unfortunately, but I will confirm that
`nothing` gets auto-converted to `None`. I'd guess that the issue is
elsewhere. You might be able to debug it further / code around the problem
by writing a Python function that accepts the Julia arguments and passes
them on to cv2.drawMatchesKnn. Then you can test various combinations and
find out which argument is the culprit.
On Friday, June 17, 2016 at 8:59:34 PM UTC-4, I Ce wrote:
>
> Thank you for the replies,Gabriel and Stefan.
>
> img3 = cv2.drawMatchesKnn(train,kp1,query,kp2, good, :none, flags=4)
>
> yields the same error:
>
> LoadError: PyError (:PyObject_Call) <type 'exceptions.SystemError'>
> SystemError('NULL result without error in PyObject_Call',)
>
> while loading In[60], in expression starting on line 22
>
> in pyerr_check at /home/-/.julia/v0.5/PyCall/src/exception.jl:56 [inlined]
> in pyerr_check at /home/-/.julia/v0.5/PyCall/src/exception.jl:61 [inlined]
> in macro expansion at /home/-/.julia/v0.5/PyCall/src/exception.jl:81
> [inlined]
> in #pycall#46(::Array{Any,1}, ::Function, ::PyCall.PyObject,
> ::Type{PyCall.PyAny}, ::Array{UInt8,2}, ::Vararg{Any,N}) at
> /home/-/.julia/v0.5/PyCall/src/PyCall.jl:510
> in (::PyCall.#kw##pycall)(::Array{Any,1}, ::PyCall.#pycall,
> ::PyCall.PyObject, ::Type{PyCall.PyAny}, ::Array{UInt8,2}, ::Vararg{Any,N})
> at ./null:0
> in #call#47(::Array{Any,1}, ::PyCall.PyObject, ::Array{UInt8,2},
> ::Vararg{Any,N}) at /home/-/.julia/v0.5/PyCall/src/PyCall.jl:522
> in (::PyCall.#kw#PyObject)(::Array{Any,1}, ::PyCall.PyObject,
> ::Array{UInt8,2}, ::Vararg{Any,N}) at ./null:0
> in include_string(::String, ::String) at ./loading.jl:380
> in eventloop(::ZMQ.Socket) at /home/-/.julia/v0.5/IJulia/src/IJulia.jl:143
> in (::IJulia.##24#30)() at ./task.jl:310
>
>
> I guess I'll open an issue on GitHub.
>
>
> On Friday, June 17, 2016 at 2:42:32 PM UTC-4, I Ce wrote:
>>
>> I am using PyCalland @pyimport cv2 to implement an OpenCV
>> feature-matching program in Julia.
>>
>>
>> I have an example of the code I want to use in *Python* (see *Brute-Force
>> Matching with SIFT Descriptors and Ratio Test* in this link:
>> http://docs.opencv.org/3.0-beta/doc/py_tutorials/py_feature2d/py_matcher/py_matcher.html
>> for
>> the full Python code.)
>>
>>
>> Everything up to the point of drawMatchesKnn() works fine, but I have
>> issues with the outImg argument when converting to Julia.
>>
>>
>> Documentation for drawMatchesKnn() is pasted below:
>> (and can also be found here:
>>
>> http://docs.opencv.org/3.0-beta/modules/features2d/doc/drawing_function_of_keypoints_and_matches.html#drawmatches
>>
>>
>> Python: cv2.drawMatchesKnn(img1, keypoints1, img2, keypoints2,
>> matches1to2[, outImg[, matchColor[, singlePointColor[, matchesMask[,
>> flags]]]]]) → outImg
>>
>> Parameter description:
>>
>> - img1 – First source image.
>> - keypoints1 – Keypoints from the first source image.
>> - img2 – Second source image.
>> - keypoints2 – Keypoints from the second source image.
>> - matches1to2 – Matches from the first image to the second one, which
>> means that keypoints1[i] has a corresponding point in
>> keypoints2[matches[i]] .
>> - outImg – Output image. Its content depends on the flags value
>> defining what is drawn in the output image. See possible flags bit values
>> below.
>> - matchColor – Color of matches (lines and connected keypoints). If
>> matchColor==Scalar::all(-1) , the color is generated randomly.
>> - singlePointColor – Color of single keypoints (circles), which means
>> that keypoints do not have the matches. If
>> singlePointColor==Scalar::all(-1) , the color is generated randomly.
>> - matchesMask – Mask determining which matches are drawn. If the mask
>> is empty, all matches are drawn.
>> - flags – Flags setting drawing features. Possible flags bit values
>> are defined by DrawMatchesFlags.
>>
>> As you can see from the sample program, the drawMatchesKnn() line in
>> Python would look like this:
>> img3 = cv2.drawMatchesKnn(train,kp1,query,kp2,good,None,flags=2) (the
>> key argument is argument 6, specified as "None")
>>
>>
>> I'm having problems because I don't really know what an equivalent,
>> working example in Julia would be.
>>
>>
>>
>> I tried this:
>> img3 = cv2.drawMatchesKnn(train,kp1,query,kp2,good)
>>
>> And got this error: (so arg6 is required)
>>
>> LoadError: PyError (:PyObject_Call) <type 'exceptions.TypeError'>
>> TypeError("Required argument 'outImg' (pos 6) not found",)
>>
>>
>>
>> This: (passing the scalar value 0, which worked for the method
>> drawKeyPoints() in another program)
>> img3 = cv2.drawMatchesKnn(train,kp1,query,kp2,good,0,flags=2)
>>
>> and got this error:
>>
>> LoadError: PyError (:PyObject_Call) <type 'exceptions.SystemError'>
>> SystemError('NULL result without error in PyObject_Call',)
>>
>>
>>
>> and this:
>> img3 = cv2.drawMatchesKnn(train,kp1,query,kp2,good,nothing,flags=2)
>>
>> and got this error:
>>
>> LoadError: PyError (:PyObject_Call) <type 'exceptions.SystemError'>
>> SystemError('NULL result without error in PyObject_Call',)
>>
>>
>> Seems tricky to me because None in Python and nothing in Julia do not
>> appear to behave the same way.
>>
>>
>> Anything else I could try? What could the problem be, and how can I fix
>> it?
>>
>>
>> Thanks for reading!
>> Any help is much appreciated.
>>
>
